Didier Drogba will now take the Brazilian's old no.11 shirt.
Returning hero Drogba will take the no.11 shirt, vacated by Oscar, who will now wear Frank Lampard's old no.8
Courtois will take up no.13, while Moses will wear Romelu Lukaku's old no.18 shirt.
Elsewhere, 19-year-old Ake has been given the no.6 shirt - no doubt a boost for his long-term future at Stamford Bridge.
And Oscar added: "Didier is a Chelsea legend and a senior player. I am happy for him to take the 11 and for me to take the 8. Lamps is another legend at this club and I hope I will be as successful in the shirt as he was."
The changes should provide confidence-boosters for those involved, with the decision to hand Oscar Lampard's old shirt number a significant sign of Jose Mourinho's trust in him.